Rotary piston machine

ABSTRACT

The rotary piston machine has a bypass channel, which is formed through two openings ( 15, 16 ) provided in a sidewall ( 6 ) of its delivery housing ( 4 ) and a channel ( 17 ) extending into this sidewall ( 6 ) in such a way that the bypass channel ( 17 ) is restricted on one side by a wall area of the sidewall ( 6 ) and on the opposite side by a channel cover ( 19 ) embedded in this sidewall ( 6 ). The housing ( 25 ) of a pressure relief valve ( 14 ) is formed cup-shaped in the channel cover ( 19 ) in whose cylindrical inner surface ( 27 ) a closing member ( 2 ) is operated piston-like. The machine which is designed from few individual parts is suitable especially for the space-saving and direct coupling in the engine space of a motor vehicle, in which its pressure relief valve ( 14 ) provided in the bypass channel overcomes the disadvantages of the rotational speed-dependent pressure difference between suction and pressure sides.

The invention concerns a rotary piston machine with a delivery housing enclosing at least two rotary pistons, restricted by two side walls parallel to each other, to which an inflow channel and at least one outflow channel is provided, in which the rotary pistons are fixed on a shaft supported in the sidewalls of the delivery housing and by a shaft passing to the outside through one of these sidewalls, and in which a pressure side of the delivery housing is connected to a suction side of the same through a bypass channel, which runs along one of these side walls and has a pressure-relief valve.

Machines of this type are known in many embodiments and applications. A summary of possible types has the title “Rotary Piston Machine”, London, Iliffe, 1965). Embodiments of such rotary piston machines are mentioned in US 1694805, in which the pressure side of the delivery housing is connected to its suction side through a bypass channel, which runs along a side wall of the delivery housing.

The invention is based on the problem to find a rotary piston machine suitable for a coupling-free, space-saving fit in the engine space of a motor vehicle that can be manufactured economically, which produces a suction or delivery value suitable for application as blower or compressor even at rotary speeds which varies over a wide range.

This problem is solved for a rotary piston machine of the type mentioned at the beginning by a sidewall containing the bypass channel acting as intermediate wall between the delivery housing and a gearbox housing containing a means for the control of the rotary piston motion.

Favourable embodiments of the invention are the subject of the dependent patent claims and have to be taken from the following description based on the drawings.

FIG. 1 shows a cross-section of an external-axis rotary piston machine having two rotary pistons passing through its inflow and outflow connections,

FIG. 2 shows a cross-section through the machine according to FIG. 1 passing at right angles to the cross-section according to FIG. 1 and containing both axes of the rotary pistons,

FIG. 3 shows a perspective representation of the rotary pistons of the machine according to FIGS. 1 and 2 with their drive shafts,

FIG. 4 shows a perspective view of a housing shell of the gearbox housing of the machine according to FIGS. 1 and 2 and

FIG. 5 shows a perspective representation of the bypass cover of the machine according to FIGS. 1 and 2 with correlated closing member and valve spring.

A rotary piston machine 1 according to the invention, made for example according to the construction according to Roots, has for the represented embodiment a delivery housing 4 manufactured from light alloy by pressure die casting process containing two rotary pistons 2,3, which is restricted by two sidewalls 5, 6 parallel to each other and a surrounding outer wall 7. One of these sidewalls 5 merges into the external wall 7 as single-piece so that a housing shell 8 is formed together with that. The other sidewall 6 of the delivery housing 4 forms a second housing shell 9 with its floor wall and is closed by a cover wall 10 parallel to it to restrict a gearbox housing 11. The air intake 12 opens out parallel to the rotational axis of the rotary pistons 2,3 in the delivery housing 4. A pressure-sided air intake 13 leads radially towards the outside on the side of the oblong or oval delivery housing 4 lying opposite.

To avoid too high a pressure drop between the suction and pressure sides of the machine for the selected application of the machine and if high rotary speeds arise due to its direct coupling with the drive system of a motor vehicle, the pressure side of the delivery housing 4 is connected to its suction side through a bypass channel 17, which has a pressure relief valve 14. This bypass channel 17 consists of, for example, two openings 15, 16 provided in the sidewall 6 of the delivery housing 4 and channel 17′ passing along this sidewall 6.

As can be seen from the representations of FIGS. 1,2 and 4, the bypass channel 17 has a channel 17′ formed as longitudinal recess in the sidewall 6 with a stepped, surrounding edge 18 for the form-fitting intake of the edge region of a channel cover 19. Besides, the channel 17′ extends at right angles to a line 22 connecting the drive shafts 20,21 of the rotary pistons 2,3. This arrangement of the channel 17′ has, besides its basic space-saving execution, the further advantage that, for arrangement of the pressure relief valve 14 at one end of the channel 17′, this is in an area not used by the gears 23,24 of the rotary piston drive of the gearbox housing 11 arranged beside the delivery housing 4.

The valve housing 25 of the pressure relief valve 14 is formed cup-shaped at one end of the channel cover 19 covering the bypass channel 17 corresponding to the representations in FIGS. 1 and 5. This encloses telescopically a closing member 26 formed as hollow piston so that the inner surface of the valve housing 25 forms a cylindrical surface 27 for this. One end of the valve spring 28 which determines the closing pressure of the pressure relief valve 14 lies on the floor 29 of the valve housing 25 and the other end on the floor 30 of the closing member 26 and is consequently enclosed between the valve housing and the closing member 26.

Since the execution of the housing of a machine, according to the invention, made of light alloy carries larger thermal expansions as against other metals, e.g. for the gears 23, 24, the drive shafts 20, 21 carrying the gears 23, 24 of the rotary pistons 2, 3 are also preferably made as hollow shafts. Their elasticity can compensate for thermal expansions easily. Moreover, this elasticity enables easily the connection to the rotary pistons 2,3 and/or gears 23,24 through a press fit and permits thereby larger manufacturing tolerances and consequently an easier manufacturing of the machine.

In a further preferred execution of a machine according to the invention, the gears 23, 24 are made of different, metallic materials, in which, for example, one is made of steel and the other of bronze. Such a pairing of materials also reduces the production of noise by the gears 23, 24 meshing with each other. 

1. Rotary piston machine with a delivery housing (4) enclosing at least two rotary pistons (2, 3), restricted by two side walls (5, 6) parallel to each other, to which at least one inflow channel and at least one outflow channel (12, 13) is provided, in which the rotary pistons (2, 3) are fixed on a shaft supported in the sidewalls (5, 6) of the delivery housing (4) and by a shaft passing to the outside through one of these sidewalls (6) (20, 21) and in which a pressure side of the delivery housing (4) is connected to a suction side of the same through a bypass channel (17), which runs along one of these side walls (6) and has a pressure-relief valve (14) characterized in that one sidewall (6) containing the bypass channel (17) acts as intermediate wall between the delivery housing (4) and a gearbox housing (11) containing the means (23,24) for the control of the rotary piston motion.
 2. Machine according to claim 1, characterized in that an area of the channel cover (19) of the bypass channel (17) is formed as valve housing (25) of a pressure relief valve (14).
 3. Machine according to claim 2, characterized in that the cup-shaped valve housing (25) telescopically encloses a closing member (26) made as hollow piston so that the housing inner wall forms a cylindrical surface (27) for this, in which a valve spring (28) which determines the closing pressure is enclosed between the two.
 4. Machine according to claim 1, characterized in that two rotary pistons (2, 3) arranged externally axially to each other are enclosed in the delivery housing (4) and their drive shafts (20, 21) extending through the intermediate wall (6) are connected to the gear wheels (23, 24) enclosed in the gearbox housing (11) meshing with each other so that these gears (23,24) form the means for the control of the rotary piston motion, in which the part of the bypass channel (17) provided on the intermediate wall (6) extends at right angles to a line (22) connecting the drive shafts (20,21) and the valve housing (25) extends into the gearbox housing (11) at the side beside the gear pair (23,24).
 5. Machine according to claim 1, characterized in that several rotary pistons (2,3) are enclosed in the delivery housing (4) and are controlled by gears (23, 24) enclosed in the gearbox housing (11) meshing with each other, which form the means for the control of the rotary piston motion, in which the shafts (20, 21) carrying a rotary piston (2,3) and a gear (23,24) are made hollow respectively.
 6. Machine according to claim 5, characterized in that one of the gears (23, 24) meshing with each other is made of steel and the other of a nonferrous metal.
 7. Machine according to claim 1 characterized in that the bypass channel (17) is formed through openings (15, 16) provided in one of the sidewalls (6) of the delivery housing and a channel (17) passing along the sidewall (6) in such a way that a part of the bypass channel (17) is restricted on one side by a wall area of the sidewall (6) of the delivery housing and on the opposite side by a channel cover (19). 